Modern telecommunication systems include heterogeneous mixtures of second, third, and fourth generation (2G, 3G, and 4G) cellular-wireless access technologies, which can be cross-compatible and can operate collectively to provide data communication services. Global Systems for Mobile (GSM) is an example of 2G telecommunications technologies; Universal Mobile Telecommunications System (UMTS) is an example of 3G telecommunications technologies; and Long Term Evolution (LTE), including LTE Advanced, and Evolved High-Speed Packet Access (HSPA+) are examples of 4G telecommunications technologies. The 5G telecommunication technologies are the next generation mobile networks that are designed to combine both an evolution and revolution of the existing LTE/LTE-A mobile networks to provide a much higher connectivity, greater throughput, much lower latency, and ultra-high reliability to support new use cases and applications. Some of mobile devices operating in such telecommunication systems are also capable of operating over Wi-Fi networks for voice, also known as Voice-over-IP (VoIP) and data.
A user of such a mobile device may occasionally receive a call from an unknown caller, which may turn out be an unwanted call such as a sales, telemarketing, robocall, spam, and the like. Even if the user had subscribed to a caller ID service, seeing an unknown telephone number might not necessarily inform the user whether the call was an unwanted call. The phone number provided by the caller ID service may even be a spoofed number by a scammer. If the user is out of coverage or is outside of the user's network, for example, while roaming, and the call is rejected or unanswered, the call is directed to the user's voicemail system where the caller may leave a voicemail, which may be unwanted.